A locking differential may have an additional capability compared to a conventional “open” automotive differential. A vehicle with a locking differential may experience increased use of traction at the drive wheels compared to a vehicle with an “open” differential. Use of traction may be increased by restricting each of the two drive wheels on an axle to the same rotational speed without regard to the available traction or the road path taken at each wheel. The locking differential causes both wheels on an axle to turn together as if on a common axle shaft.
An open differential, or unlocked locking differential allows each wheel on an axle to rotate at different speeds. When a vehicle negotiates a turn, the wheel on the smaller (inner) radius rotates more slowly than the wheel on the larger (outer) radius. Without the unlocked or open differential, one of the tires may scuff in a turn. With an open differential, when one wheel of an axle is on a slippery road surface, the wheel on the slippery surface may tend to spin while the other wheel may not have enough torque applied to it to move the vehicle. For example, some vehicles with open differentials may be unable to climb a hill with wet ice under one of the wheels no matter how dry the pavement is under the other wheel (this may be known as a split-mu surface).
In contrast, a locked differential forces wheels on both sides of the same axle to rotate together at the same speed. Therefore, each wheel can apply as much torque as the wheel/road traction and the powertrain capacity will allow. In the example of the vehicle on the hill with the split-mu surface, a locked differential may allow the vehicle to climb the hill that is impossible for an otherwise identical vehicle to climb with an open differential. Locking differentials may also provide better traction that leads to improved vehicle performance under certain conditions, for example in drag racing, or snow plow operations.
Some vehicles have differentials that may be reconfigured from an unlocked state to a locked state. Such vehicles may be operated with the differential in the unlocked state for normal conditions, for example, to prevent tire scuffing in turns, and reconfigured for operation with a locked differential when wheel slippage is encountered.